The production of trichomes can be observed in many species of plants throughout nature, taking on various physical forms as well as serving many different purposes. For example, trichomes found on some carnivorous plants aid in helping to catch prey. In Cannabis, trichomes function as a defense mechanism. When female Cannabis plants begin to produce flowers in the wild, they often become vulnerable to various insects and animals as well as non-living environmental variables such as potentially harmful UV rays. Trichomes serve as a deterrent for animals because their bitter taste and strong aromas render Cannabis flowers unpalatable. At the same time, they also serve a dual function in protecting their plants from damaging winds and even some varieties of fungal growth. Bulbous trichomes are the smallest of the bunch, and they appear on the surface of the entire plant. Bulbous trichomes are as small as 10-15 micrometers, which is tiny enough to only be comprised of a handful of cells. Capitate sessile trichomes are slightly larger and contain both a head and a stalk. Capitate-stalked trichomes range from anywhere between 50-100 micrometers wide, meaning they're much larger and can actually be seen by the naked eye. Their structure consists of a stalk comprised of epidermal and hypodermic cells that build up to a basal cell which attaches to a large gland head. This gland head, held together by a waxy cuticle layer, serves as the epicenter for cannabinoid and terpenoid synthesis.
The importance of the process of extraction has increased with the growing global awareness of the medicinal, wellness and nutritional benefits of Cannabis plant extracts. In the example of hemp species of Cannabis it has been discovered that compounds present on the plant provide medicinal benefit for such conditions as inflammation, pain, nausea and epilepsy. There are some 60 bio-active compounds within the Cannabis plant. Some of these compounds are predicted to be valuable natural-source drugs which may not be associated with the side effects which plague commercial synthetic drugs.
Various methods of solvent extraction have been developed to separate the cannabinoids and terpenes from the non-cannabinoid and terpene biomaterial. Concentration of the cannabinoids and terpenes by solvent extraction is widely practiced and allows for the development of a wide variety of consumer products such as cannabinoid containing baked goods, gummies, sprays, drinks and other forms of cannabinoid products.
Industry has evolved three primary methods of solvent extraction including but not limited too super critical carbon dioxide, cold ethanol extraction and compressed butane extraction. Typical industrial practice is to first dry the fresh harvested whole plant material to about 5% to 10% moisture from a starting moisture greater than 50%. Then the biomass is processed, usually by hand or a semi-automated process where each plant is individually fed into into a machine by hand, to separate the plant stem and fan leaves from the flower and cannabinoid rich leaves. The flower and leaf material is then typically subjected to one of the 3 common extraction methods to obtain the cannabinoids and remaining terpenes from the dried plant.
For example, in Method for Continuous Extraction and Separation of Useful Compounds from Plant or Animal Material Patent Literature U.S. Pat. No. 6,403,126, Webster et al teaches a method of extracting cannabinoids, cannflavins or essential oils in which the solvent may be a petroleum-derived hydrocarbon (for example: toluene or trimethylpentane); a low molecular weight alcohol (for example ethanol); a low molecular weight chlorinated hydrocarbon (for example, choroform); dichloromethane; or, supercritical fluid such as CO2; and various products from hemp lacking A9-THC obtained by passing the extract over a chromatographic column. U.S. Pat. No. 9,782,691, Chess et al teaches a process in which super- or sub-critical CO2 is, alone or with a lower vapor pressure gas or gases, collected and re-used in a closed-loop extraction process. U.S. Pat. No. 9,399,180, Ellis et al teaches a vertical extraction process in which liquid gas is applied at the top, a vacuum draws down the extractant, and the gas is removed by cooling and recycled. U.S. Pat. No. 8,048,304, Walbel et al teaches a process for increased efficiency in the recovery and recycle of gases used in an extraction process. U.S. Pat. No. 9,358,259, Hospodor et al teaches a process of extracting cannabinoids in which the solvent is passed through the material many times in a cycle, the extractant remaining behind in a collector tank from which the solvent is removed and recycled. U.S. Pat. Nos. 9,669,328, 9,789,147, and 9,844,740, Jones, teach a process of extraction in which extraction takes place using liquid gases after which the product is used as is. The methods described lack the ability to extract cannabinoids and terpenes from the surface trichomes of whole wet plant material.
Hemp-derived cannabinoid use is rapidly expanding and more effort must be made to improve the extraction efficiency and overall extraction process economics. The current method of hand harvesting the hemp followed by drying and physical processing of the plant to remove stem and fan leaves is very costly, labor intesive and impractical when considering hand harvesting and drying thousands of acres and millions of pounds of biomass. Current extraction processes and methodology must be adapted for efficiency to modern outdoor farming and crop harvest methods. The ability to harvest the hemp biomass mechanically and process the plant in its intact and wet form will dramatically reduce the costs for growers, processors and consumers. Clearly a method of extracting cannabinoids and terpenes from whole plant wet biomass is needed.